    nobshcL(1+r)(1+v)16i=1iB(cXi)B(hcc),


where \(n^{\rm obs}_{h_{c}}\)  is the number of observed \(h_{c}\)  signal
events; \({\cal L}\)  is the integrated luminosity; \((1+\delta ^{r})\)  is
the initial radiative correction factor, which is taken to be the same
as that for the analysis of \(e^+e^-\rightarrow \pi ^+\pi ^-h_c\)  [1]};
\((1+\delta ^{v})\)  is the vacuum polarization factor [2]};
\(\epsilon _i\)  is the detection efficiency for the \(i^{th}\)
\(\eta _c\)  decay mode in the decay \(e^+e^-\rightarrow \pi ^{0}\pi ^0 h_c\)  without
consideration of any possible intermediate structures and with ISR and
vacuum polarization effects considered in the MC simulation; \({\cal B}(\eta _c\rightarrow X_i)\)  is the corresponding \(\eta _c\)  branching fraction;
\({\cal B}(h_c\rightarrow \gamma \eta _c)\)  is the branching fraction of
\(h_c\rightarrow \gamma \eta _c\) .
